Kinetics of thermal decomposition have always played an important role in metallurgy and processing of raw materials. Introduction of kinetic models of thermal dissociation leads to considerable simplification of running of such processes. The following stages may control the rate of product formation: -chemical reaction at an interface; - nucleation; - diffusion of reactants of fast chemical reactions. The controlling factor may change during the course of reaction. Measurements at non-isothermal conditions were chosen to determine the kinetic parameters (as such conditions are closer to those which occur in a real technical process). Various methods of description of non-isothermal decomposition of solids were discussed. There were analysed various functions f(alpha) describing the kinetics of decomposition of solids. The methods based on one kinetic curve analysis (approximation, differential and integral methods) and those based on several kinetic curves (Kissinger method, isoconversional methods in a differential form (Fridmann), and in an integral form (Ozawa, Flynn-Wall)) were discussed. It was found that various approaches to solve temperature integrals which had been used led to the same values of kinetic parameters. The Coats-Redfern method was the simplest one. It is frequently used to describe the kinetics of thermal decomposition of solids. As a model substance carbonate calcium was used. Although numerous papers-on the kinetics and mechanism of such reactions have been published, the important problem of inconsistency in values of kinetic parameters obtained by various authors has not been solved so far. Thermal analysis of CaCO3 has been carried out using a derivatograph (MOM-1500, Budapest) under the air. CaCO3 dissociated into CaO and CO2 starting from about 580 degrees C and giving an endothermic band with the maximum at 820 degrees C. From the mass loss observed by means of the TG-curves the alpha-T relations were estimated. The curves obtained were processed by a special computer program based on the method of the least-squares. Basing on the alpha(T) dependence the g(alpha) functions, from the well-known kinetic models which best described the experimental results, were chosen. The values of activation energy and preexponential factor in the Arrhenius equation as well as entropy, enthalpy and free energy of activation were calculated from the Eyring equation. The correlation coefficient standard deviation and Snedecor＇s variable were calculated to aid selections of the g(alpha) function. We have found that the thermal decomposition of CaCO3 is mainly controlled by diffusion (models D2, D4) however the contracting area model R2 is also possible to be applied. The activation energy of the decomposition process was 352 kJ . mol(-1) for the D2 model, 360 KJ . mol(-1) for the D4 model and 165 kJ . mol(-1) for the R2 model. It was found that the best results were obtained basing on the integral and differential methods, which were the most accurate. It was proved that the rate of heating did not influence the values of kinetic parameters. It was also shown that the values of free energy of activation were independent of the model having been assumed, varying only in division on the part connected with E and A or Delta H* and Delta S*.